Gas turbine engines are often used as a power source in machines. Typical gas turbine engines may use a compressor to provide compressed air to a combustor, and fuel may be injected into the combustor by a fuel injector. The compressed air may be mixed with fuel in the combustor and may be ignited by conventional means to generate combustion gasses. The combustion gasses may be discharged from the combustor into a conventional turbine, which may extract energy from the gasses to power various components of the engine and/or machine.
During operation, temperatures within the combustor may increase due to the exothermic combustion of the fuel/air mixture. The highest temperatures may be experienced by components located proximate the fuel injector. The components of the combustor closest to the fuel injector may, thus, experience the greatest increase in temperature, while those shielded and/or further removed from the injector may experience a smaller increase. Due to this larger increase in temperature, the components closest to the injector may also experience greater thermal expansion than the shielded components. As a result of the different levels of thermal expansion experienced by the combustor components, directly connecting these components to each other may cause damage to the components over time and may reduce the active life of the combustor. In conventional gas turbine engines, combustor components may be connected together indirectly so as to allow for relative movement of the components. Such engines may also cool the combustor components through conventional impingement cooling methods wherein jets of cooling air are directed onto hot components of the combustor.
For example, U.S. Pat. No. 5,291,732 to Halila (“the '732 patent”) describes a combustor having a casing, a frame, and a liner. The frame is rigidly connected to combustor casing and is configured to support the liner within the casing. The liner is joined to the frame by pins extending through holes in the liner. Other combustor components are also joined to the frame by the pins, and the pins allow differential thermal expansion and contraction between the components connected thereto. The pins are disposed away from the combustion zone, in a relatively cool region of the combustor. In this region, the components may experience a relatively small difference in thermal expansion, whereas the same components may experience a much larger amount of expansion closer to the combustion zone.
Although the assembly described in the '732 patent may allow for relative movement between the different components of the combustor due to varying amounts of thermal expansion, connecting the components upstream of the combustion zone may result in high thermal stresses on the pinned components during operation of the combustor. These high thermal stresses may occur as a result of the difference in temperature between the combustion zone and the relatively cool region of the combustor where the components are pinned. Such stresses may cause failure in combustor components made of materials having a high coefficient of expansion. To avoid such stress-induced failures, materials having lower coefficients of expansion may be used as an alternative. Such materials, however, may be expensive and may increase the overall cost of the combustor.